Improvement in processes for removing extractive matters from tanned leather



UNITED STATES PATENT'OFFIGE.

GEORGE PLUMER AND OHARLES P. KERANS, OF PEABODY, MASS.

IMPROVEMENT m PROCESSES FOR REMOVING EXTRACTIVE MATTERS FROMi'l'ANNEDLEATHER.

Specification forming part of Letters Patent No. 221,187, dated November4, 1879; application filed July 21, 1879.

, in g tannin and extractive matters from tanned leather in order tosoften and uniformly cleanse the tanned leather preparatory to againretanning and giving-to the same the desired color by subsequentoperations.

Tanned leather, as now commonly 7 made, when removed from the firsttannin g-solution, is very apt to be of uneven color by reason of thepresence in the hide of too much lime or extractive or otherobjectionable matter added thereto in the tanning process, which.matters, if not removed, make it quite difficult, if not impossible, togive to the leather by subsequent treatment a light or uniform color.

In this our invention leather tanned in any of the usual ways, as by thehemlock or oak tanned or other usual processes, is subjected to theaction of a cleansing-bath, which thoroughly removes from the tannedhide the extractive and tanning substances, and grease or tannate oflime, and such other objectionable substances added to the hide duringthe liming, bating, and first tanning processes, especially all suchmatter as would tend to make the finished leather hard or brittle oruneven in color, or which would interfere with giving to the grain-faceof the finished leather a light even color. This we accomplish in thefollowing manner, viz: The tanned leather, say, twenty-five sides,containing from twenty to twenty-five feet each, are subjected in a millto the action of diluted solution of borax for from ten to fifteenminutes, moreor less. We take for the quantity of leather mentionedabout six pounds of borax dissolved in about thirty gallons of Water.

In practice we have obtained the best results by the use of what iscommonly known as the England wheel, it-being a closed circular orboxlike wheel of, say, about eight feet diameter by from two to threefeet in widt11,it having a hollow journal for the entrance of a water orsteam pipe, and a side door for the introduction and removal of theleather, the door being suitably packed to obviate leakage.

Having added the borax-water to the wheel, and having placed the tannedleather therein, the wheel is rotated at the rate, say, of about sixteenrevolutions per minute for about fifteen minutes, more or less, or untilthe objectionable matters hereinbefore referred to are loosened, when ahose or other water-supp] y pipe is added to the hollow journal of thesaid wheel or mill to lead water into the wheel and in contact with theleather, so as to, by a continuous flow of water in and through thewheel and over the leather, wash out therefrom the borax and all theother objectionable matters loosened or started by the first millingoperation in the borax-water. This treatment leaves the leather inproper and the best possible and most favorable condition to be retannedfor all leather where softness and lightness of color are desired. 1

We have mentioned the use of a wheel-like mill having a horizontal axle;but it'is obvious that any other usual or suitable mill capable ofagitating the leather in this borax solution would answer all practicalpurposes.

We claim- That improvement in the art or process of treatingtannedleather preparatory to retanning the same which consists in subjectingthe tanned leather to the action of a solution of borax and water,substantially as and for the the purpose herein set forth.

In testimony whereof we have signed our names to this specification inthe presence of two subscribing witnesses.

GEO. PLUMER. CHARLES P. KERANS.

Witnesses G. W. GREGORY, N. E. WHITNEY.

